Sena, M.G., M. Peipoch, B. Joshi, M.M. Rahman, E. Peck, A.J. Gold, J. Kan, and S. Inamdar. 2025. Journal of Geophysical Research Biogeosciences 130(2): e2023JG007900.
Plain Language Summary
Wetland or riparian soils and groundwaters depleted of oxygen can accumulate ammonium–N (NH4+), a toxic pollutant at high concentrations. NH4+ can be produced and removed via microbial processes that are influenced by seasonal factors such as: temperature, groundwater levels, dissolved oxygen, organic carbon, nitrate, and dissolved iron. In this study, we studied monthly grab samples of riparian groundwater collected upstream of milldams over a period of 4 years. We evaluated the data, identified three main seasons, and generated relationships between physical and chemical factors and NH4+ over time. The main findings from this study show that NH4+: (a) peaks in October and November when water is warm, stagnant, and high in organic carbon, (b) decreases from January – April when temperatures cooled and lowered microbial production, and (c) elevated iron groundwater concentrations can dampen these seasonal trends. Results from this study can help to improve the timing of milldam removal practices and for the management of wetlands that remove nitrogen from the terrestrial environment.